Sodium sulfide leach process

Abstract

A process is disclosed for treating mixed metal sulfides containing trivalent antimony sulfide wherein the sulfide concentrates are leached with an excess of sodium sulfide in order to isolate copper sulfide and other insolubles in solid form while solubilizing the remaining metal sulfides and producing sodium thioantimonite, separating the insoluble sulfides from the solution; oxidizing the sodium thioantimonite with elemental sulfur to produce sodium thioantimonate in solution; crystallizing a portion of the sodium thioantimonate along with other available metal sulfides from solution; and recirculating the remainder of the solution to the sodium sulfide leach stage. The crystallized metal sulfides may be further treated, isolated, and recovered as desired.

What is claimed is: 
     
       1. A process for treating metal sulfides in the presence of antimony sulfide comprising: a. leaching the metal sulfides with sodium sulfide in order to produce a residue containing insoluble sulfides and a solution comprising sodium thioantimonite and the remaining metal sulfide values;   b. separating the insoluble metal sulfides from the solution;   c. oxidizing the sodium thioantimonite in solution to sodium thioantimonate;   d. crystallizing a portion of the sodium thioantimonate from the solution; and   e. separating the crystallized sodium thioantimonate from the solution.   
     
     
       2. The process of claim 1 wherein the metal sulfides being treated include chalcopyrite. 
     
     
       3. The process of claim 1 wherein the antimony sulfide comprises one or more members selected from the group consisting of tetrahedrite and stibnite. 
     
     
       4. The process of claim 1 wherein the metal sulfides being treated include arsenopyrite. 
     
     
       5. The process of claim 4 wherein the metal sulfides being treated are initially roasted within a temperature of from about 400° C to about 600° C. 
     
     
       6. The process of claim 1 wherein the metal sulfides being treated include gold. 
     
     
       7. The process of claim 6 comprising: a. redissolving the crystallized sodium thioantimonate;   b. adjusting the pH of the solution resulting from the redissolving of the crystals to about 12;   c. contacting the redissolved sodium thioantimonate solution with an ion exchange agent loaded onto an activated carbon surface, the ion exchange agent comprising: ##STR2##  wherein R is a mixture of C 8  and C 10  carbon chains, in order to remove substantially all of the gold from solution.   
     
     
       8. The process of claim 1 wherein the metal sulfides being treated include arsenic sulfides. 
     
     
       9. The process of claim 8 comprising: a. redissolving the crystallized sodium thioantimonate to form a solution comprising sodium thioantimonate and sodium thioarsenate;   b. subjecting the sodium thioantimonate/sodium thioarsenate solution to partial oxidation by injecting sufficient oxygen so as to maintain a final solution e.m.f. of from about 300 millivolts to about 500 millivolts, measured with Platinum/saturated Calomel electrodes while maintaining the product solution at a pH of from about 7 to about 11 in order to oxidize and precipitate a substantial portion of the sodium thioantimonate as antimony sulfide while leaving substantially all of the sodium thioarsenate in solution.   
     
     
       10. A process for treating metal sulfides including gold in the presence of antimony sulfide comprising: a. leaching the metal sulfides with sodium sulfide in order to produce a residue containing insoluble sulfides and a solution comprising sodium thioantimonite and the remaining metal sulfide values;   b. separating the insoluble metal sulfides from the solution;   c. oxidizing the sodium thioantimonite in solution to sodium thioantimonate;   d. crystallizing a portion of the sodium thioantimonate from the solution;   e. separating the crystallized sodium thioantimonate from the solution;   f. redissolving the crystallized sodium thioantimonate;   g. adjusting the pH of the solution resulting from the redissolving of the crystals to about 12;   h. contacting the redissolved sodium thioantimonate solution with an ion exchange agent loaded onto an activated carbon surface, the ion exchange agent comprising: ##STR3##  wherein R is a mixture of C 8  and C 10  carbon chains, in order to remove substantially all of the gold from solution.   
     
     
       11. A process for treating metal sulfides including arsenic sulfides in the presence of antimony sulfide comprising: a. leaching the metal sulfides with sodium sulfide in order to produce a residue containing insoluble sulfides and a solution comprising sodium thioantimonite and the remaining metal sulfide values;   b. separating the insoluble metal sulfides from the solution;   c. oxidizing the sodium thioantimonite in solution to sodium thioantimonate;   d. crystallizing a portion of the sodium thioantimonate from the solution;   e. separating the crystallized sodium thioantimonate from the solution;   f. redissolving the crystallized sodium thioantimonate to form a solution comprising sodium thioantimonate and sodium thioarsenate;   g. subjecting the sodium thioantimonate/sodium thioarsenate solution to partial oxidation by injecting sufficient oxygen so as to maintain a final solution e.m.f. of from about 300 millivolts to about 500 millivolts, measured with platinum/saturated Calomel electrodes while maintaining the product solution at a pH of from about 7 to about 11 in order to oxidize and precipitate a substantial portion of the sodium thioantimonate as antimony sulfide while leaving substantially all of the sodium thioarsenate in solution.   
     
     
       12. A process for treating metal sulfides in the presence of antimony sulfide comprising: a. leaching the metal sulfides with sodium sulfide in order to produce a residue containing insoluble sulfides and a solution comprising sodium thioantimonite and the remaining metal sulfide values;   b. separating the insoluble metal sulfides from the solution;   c. oxidizing the sodium thioantimonite with elemental sulfur in solution to produce sodium thioantimonate;   d. crystallizing a portion of the sodium thioantimonate from the solution; and   e. separating the crystallized sodium thioantimonate from the solution.   
     
     
       13. The process of claim 12 wherein the reaction is conducted within a temperature range of from about 20° C to about 200° C. 
     
     
       14. The process of claim 12 wherein the reaction is conducted within a temperature range of from about 50° C to about 100° C. 
     
     
       15. The process of claim 12 wherein the reaction is conducted for a period of time of between about 0.1 and about 10 hours. 
     
     
       16. The process of claim 12 wherein the reaction is conducted for a period of time of between about 0.25 and about 0.5 hours.